Evolution of the Iberian Massif as deduced from its crustal thickness and geometry of a mid-crustal (Conrad) discontinuity

Abstract. Normal incidence seismic data provide the best images of crust and lithosphere. When properly designed continuous, these sections greatly contribute to understanding geometry orogens and, along with surface geology, unraveling their evolution. In this paper we present most complete transect, date, Iberian Massif, westernmost exposure European Variscides. Despite heterogeneity dataset, acquired during last 30 years, resulting from reprocessing a homogeneous workflow allow us clearly define crustal thickness its internal architecture. The Massif crust, formed by amalgamation continental pieces belonging Gondwana Laurussia (Avalonian margin), is well structured in upper lower crust. A conspicuous mid-crustal discontinuity defined top reflective asymptotic reflections that merge into it, suggesting it has often acted as detachment. position can give insights evolution orogen (i.e., magnitude compression effects extent later-Variscan gravitational collapse). Moreover, limited below, central northwestern Iberia, might have constrained response microplate Alpine shortening. Here, discontinuity, featuring Vp (P-wave velocity) increase, observed an orogen-scale boundary characteristics compatible those globally debated Conrad discontinuity.